pub fn describe_nonlinear_term(
arena: &ExprArena,
id: ExprId,
resolve: &impl Fn(VarId) -> String,
) -> Option<String>Expand description
Render the first nonlinear summand of id as a short infix string, resolving
each VarId to a display name via resolve. Returns None when id is
fully affine (no nonlinear residual).